Towards Low Energy Physics from the Heterotic String

We investigate orbifold compactifications of the heterotic string, addressing in detail their construction, classification and phenomenological potential. Based on the insight gained from grand unification theories, we develop a successful strategy to search for models resembling the minimal supersymmetric extension of the standard model (MSSM) in Z_6-II orbifold compactifications. We find about 200 MSSM candidates with the gauge group and the exact spectrum of the MSSM, and supersymmetric vacua below the compactification scale. Among them, there are several models with the following realistic features: R-parity, seesaw suppressed neutrino masses, and intermediate scale of supersymmetry breakdown.</p

Low Energy Supersymmetry from the Heterotic Landscape

We study possible correlations between properties of the observable and hidden sectors in heterotic string theory. Specifically, we analyze the case of the Z6-II orbifold compactification which produces a significant number of models with the spectrum of the supersymmetric standard model. We find that requiring realistic features does affect the hidden sector such that hidden sector gauge group factors SU(4) and SO(8) are favoured. In the context of gaugino condensation, this implies low energy supersymmetry breaking.Comment: 4 pages, 3 figures; to appear in Phys. Rev. Let

La poca eficacia de los Sistemas de Recaudación Fiscal ante la falta de Regulación Jurídica en El Salvador.

Se aborda una serie de temas que se relacionan con la problemática en estudio, es decir, la poca eficacia de los sistemas de recaudación fiscal ante la falta de regulación jurídica en El Salvador, dentro de los cuales se desarrollan, que es necesario tener conocimiento sobre los diferentes sistemas tributarios que existen así como también de los aspectos generales que los rodean, para tener un mejor entendimiento sobre lo todo lo que implica llevar acabo la recaudación fiscal ya que si esto no se hace el Estado no podría satisfacer las necesidades básicas que la población presenta. También se desarrolla un Sistema Tributario, que es el conjunto de impuestos sistematizados entre sí, que se regulan en El Salvador, en un determinado espacio y tiempo. Las dificultades para hacer efectivo el pago de las multas, pago a cuenta e impuestos, son los principales problemas con la que se encuentran los contribuyentes, así como los diferentes conflictos que se dan dentro del ministerio de Haciendo específicamente en la Dirección General de impuesto Internos con la Dirección General Tributaria. El problema en El Salvador es que los contribuyentes no están orientados para realizar sus obligaciones por la escasez de cultura tributaria que poseen, esto se puede observar, en el momento de percatarse de la cantidad de contribuyentes que se aglutinan en los dos últimos días de presentación y pago del impuesto, de igual forma se puede denotar en la costumbre de no pedir facturas por la realización de las compras, entre otros aspectos, contribuyendo con ello a la falta de ingresos, que tiene los fondos del Estado

Exploring the SO(32) Heterotic String

We give a complete classification of Z_N orbifold compactification of the heterotic SO(32) string theory and show its potential for realistic model building. The appearance of spinor representations of SO(2n) groups is analyzed in detail. We conclude that the heterotic SO(32) string constitutes an interesting part of the string landscape both in view of model constructions and the question of heterotic-type I duality.Comment: 21 pages, 5 figure

Low-cost oblique illumination: an image quality assessment

P. 1-14We study the effectiveness of several low-cost oblique illumination filters to improve overall image quality, in comparison with standard bright field imaging. For this purpose, a dataset composed of 3360 diatom images belonging to 21 taxa was acquired. Subjective and objective image quality assessments were done. The subjective evaluation was performed by a group of diatom experts by psychophysical test where resolution, focus, and contrast were assessed. Moreover, some objective nonreference image quality metrics were applied to the same image dataset to complete the study, together with the calculation of several texture features to analyze the effect of these filters in terms of textural properties. Both image quality evaluation methods, subjective and objective, showed better results for images acquired using these illumination filters in compari-son with the no filtered image. These promising results confirm that this kind of illumination filters can be a practical way to improve the image quality, thanks to the simple and low cost of the design and manufacturing process.S

Lights and pitfalls of convolutional neural networks for diatom identification

P. 1-10Diatom detection has been a challenging task for computer scientist and biologist during past years. In this work, the new state of art techniques based on the deep learning framework have been tested, in order to check whether they are suitable for this purpose. On the one hand, RCNNs (Region based Convolutional Neural Networks), which select candidate regions and applies a convolutional neural network and, on the other hand, YOLO (You Only Look Once), which applies a single neural network over the whole image, have been tested. The first one is able to reach poor results in out experimentation, with an average of 0.68 recall and some tricky aspects, as for example it is needed to apply a bounding box merging algorithm to get stable detections; but the second one gets remarkable results, with an average of 0.84 recall in the evaluation that have been carried out, and less aspects to take into account after the detection has been performed. Future work related to parameter tuning and processing are needed to increase the performance of deep learning in the detection task. However, as for classification it has been probed to provide succesfully performance.S

Especies de picudos (Coleoptera: Curculionidae) asociados a limón persa en Tabasco, México

Weevils (Coleoptera: Curculionidae) are one of the main pests in citrus production systems due to their distribution and way of feeding. The objective of this work was to morphologically identify the species of weevils associated with the cultivation of Persian lime (Citrus latifolia Tanaka) in the citrus zone of the municipality of Huimanguillo, Tabasco, Mexico. The captures of weevils were made directly in the canopy, from September 2019 to February 2021, for a total of 17 collected in three Persian lemon plantations, two with conventional management and one with organic management, each one with useful plots of two hectares (624 plants). A total of 1,039 weevils corresponding to four morphospecies were collected, of which 240 were morphologically identified as Epicaerus sp. (1), 355 as Epicaerus sp. (2), 112 as Exophthalmus opulentus and 332 as Cleistolophus subfasciatus.Los picudos (Coleoptera: Curculionidae) son una de las principales plagas en los sistemas de producción citrícola debido a su distribución y forma de alimentación. El objetivo del presente trabajo fue identificar morfológicamente las especies de picudos asociados al cultivo de limón persa (Citrus latifolia Tanaka) en la zona citrícola del municipio de Huimanguillo, Tabasco, México. Las capturas de picudos se realizaron de manera directa en la copa de los árboles, de septiembre de 2019 a febrero de 2021, para un total de 17 muestreos en tres plantaciones de limón persa, dos con manejo convencional y una con manejo orgánico, cada una con parcelas útiles de dos hectáreas (624 plantas). Se colectaron 1,039 picudos correspondientes a cuatro morfoespecies, de las cuales 240 se identificaron morfológicamente como Epicaerus sp. (1), 355 como Epicaerus sp. (2), 112 como Exophthalmus opulentus y 332 como Cleistolophus subfasciatus

Moduli fixing in semirealistic string compactifications

Heterotic orbifold compactifications yield a myriad of models that reproduce many properties of the supersymmetric extension of the standard model and provide potential solutions to persisting problems of high energy physics, such as the origin of the neutrino masses and the strong CP problem. However, the details of the phenomenology in these scenarios rely on the assumption of a stable vacuum, characterized by moduli fields. In this note, we drop this assumption and address the problem of moduli stabilization in realistic orbifold models. We study their qualities and their 4D effective action, and discuss how nonperturbative effects indeed lift all bulk moduli directions. The resulting vacua, although still unstable, are typically de Sitter and there are generically some quasi-flat directions which can help to deal with cosmological challenges, such as inflation.Comment: Prepared for the XIV Mexican School on Particles and Fields, Morelia, Mexico, Nov. 4-12, 2010; 9 pages, 3 figures. v2: minor corrections, references adde

A Mini-Landscape of Exact MSSM Spectra in Heterotic Orbifolds

We explore a ``fertile patch'' of the heterotic landscape based on a Z_6-II orbifold with SO(10) and E_6 local GUT structures. We search for models allowing for the exact MSSM spectrum. Our result is that of order 100 out of a total 3\times 10^4 inequivalent models satisfy this requirement.Comment: 13 pages, for associated information see http://www.th.physik.uni-bonn.de/nilles/Z6IIorbifold/, v2: matches version published in PL

(Non-)Abelian discrete anomalies

We derive anomaly constraints for Abelian and non-Abelian discrete symmetries using the path integral approach. We survey anomalies of discrete symmetries in heterotic orbifolds and find a new relation between such anomalies and the so-called `anomalous' U(1).Comment: 32 pages, one figure; v2: matches version published in NP